Electromagnetic (EM) tissue characterization is a well known technique that utilizes an EM sensor to induce EM fields, of various frequency ranges, for example: constant (DC), low frequency, intermediate frequency, high frequency, radio frequency (RF) and microwave (MW) range, within a tissue and to receive therefrom EM response indicative of certain properties (e.g. dielectric properties) of the tissue portion located within a measurement region. The induced EM fields within the tissue may be near fields, or radiating fields. The EM response of the tissue might be characterized by certain EM resonance frequencies associated with the sensor-tissue coupling, or alternatively may be a broad band EM response (non-resonating) associated with the sensor-tissue coupling. Generally, the response of the tissue (or other medium/substance as the case may be) to EM fields is associated with the dielectric properties of the tissue, the response being characterized by, for example, absorbance, reflectance and/or transmittance of EM fields of different frequencies. Detection and analysis of the EM response of the tissue provides for differentiating between different tissue types.
Typically, EM tissue characterization sensors are configured as a spatial configuration of conductors that are connected with signal transmission lines, configured for carrying EM signals from an electromagnetic signal generator to the tissue to be characterized, and for carrying EM signals back from the tissue to be characterized to a signal analyzer.
For example, U.S. Pat. No. 6,813,515, assigned to the assignee of the present application, describes a probe, method and system for examining tissue, in order to differentiate it from other tissues, according to its dielectric properties. The method is of generating an electrical fringe field in the examined tissue to produce a reflected pulse therefrom with negligible radiation penetrating into the tissue itself; detecting the reflected electrical pulse; and comparing electrical characteristics of the reflected electrical pulse with respect to the applied electrical pulse to provide an indication of the dielectric properties of the examined tissue. The measuring device is built as a coaxial probe with cavity at its distal tip with respect to operator where a sample of the tissue to be examined is confined The probe itself has an inner conductor insulated from, and enclosed by, an outer conductor open at one end and extending past the inner conductor in the axial direction, defining an open cavity at the distal end of the probe with respect to the operator. The inner conductor includes a tip within the open cavity, which tip is formed with at least two different diameters for enhancing the electrical fringe field.
Some other examples of the tissue characterization sensors are described in the patent publications: U.S. Pat. Nos. 6,380,747; 5,227,730; 5,334,941; 6,411,103. Also, some sensors are exemplified in WO 06/103665 assigned to the assignee of the present application.
The use of an arrangement of multiple tissue characterization sensors is described for example in US 2008/0200803. Here, a cancer detection and treatment instrument is described. The instrument comprises: a first conductive plate; a second conductive plate which is opposed to the first conductive plate and has a first opening; a first signal line disposed between the first conductive plate and the second conductive plate; a first contact member of which one end is exposed through the first opening and of which the other end is connected to the first signal line; a dielectric portion filled between the first and second conductive plates and the first signal line; and a conductive layer surrounding both side surfaces and a front end surface of the dielectric portion which are exposed. Therefore, it is possible to accurately detect cancer by the use of the ultra high-frequency signal and to treat a diseased portion without damaging tissues around the diseased portion.
Some examples of how an array of sensors can be used for tissue characterization are described in WO 2009/010960 assigned to the assignee of the present application.